Information recording medium and optical information recording/reproducing apparatus

Abstract

An information recording medium includes a substrate and a recording portion having recording layers on the substrate, wherein the recording portion is capable of three-dimensional recording by changing an optical constant of the recording layers by irradiation of recording light, and a first reflected-light reducing portion for reducing reflected lights of reproducing light from the substrate side is provided at a side opposite to an incident side of the reproducing light with respect to the recording portion, and an optical information recording/reproducing apparatus records and reproduces information to and from the medium.

1. An information recording medium, comprising:
 a substrate, 
 a recording portion disposed on the substrate and including a recording layer, the recording layer having an optical constant, and 
 a first reflected-light reducing portion for reducing reflected light of a reproducing light from a substrate side, 
 wherein the recording portion is capable of three-dimensionally recording a recording pit by changing the optical constant of the recording layer by an irradiation of recording light, 
 the first reflected-light reducing portion is disposed at a side opposite to an incident side of the reproducing light with respect to the recording portion, and 
 the recording layer has no tracking guide grooves, and a tracking guide layer is disposed between the substrate and the recording portion. 
 
     
     
       2. An information recording medium according to  claim 1 , wherein the first reflected-light reducing portion includes a light absorbing portion having an optical characteristic of absorbing the reproducing light. 
     
     
       3. An information recording medium according to  claim 1 , wherein the first reflected-light reducing portion includes a reflectance reducing portion having an optical characteristic of reducing a reflectance of the reproducing light. 
     
     
       4. An information recording medium according to  claim 2 , wherein the substrate acts as the light absorbing portion. 
     
     
       5. An information recording medium according to  claim 2 , wherein the light absorbing portion includes a light absorbing layer formed between the substrate and the recording portion. 
     
     
       6. An information recording medium according to  claim 2 , wherein the light absorbing portion includes a light absorbing layer formed at a side opposite to an incident side of the reproducing light with respect to the substrate. 
     
     
       7. An information recording medium according to  claim 1 , wherein the recording portion has a multilayer structure in which recording layers and intermediate layers are alternately laminated. 
     
     
       8. An information recording medium according to  claim 1 , wherein the entire recording portion constitutes one recording layer. 
     
     
       9. An information recording medium according to  claim 1 , wherein the first reflected-light reducing portion has an optical characteristic of reducing reflected light of the recording light from the substrate side. 
     
     
       10. An information recording medium according to  claim 1 , further comprising a protection layer at an incident side of the reproducing light with respect to the recording portion. 
     
     
       11. An information recording medium according to  claim 5 , wherein, the recording layer has no tracking guide grooves, a tracking guide layer is disposed between the light absorbing layer and the substrate, and the light absorbing layer has an optical characteristic of permitting the transmission of a tracking-guide irradiating light and a tracking-guide reflected light. 
     
     
       12. An information recording medium according to  claim 2 , wherein, the light absorbing portion contains a light absorbing material having an optical characteristic of absorbing the reproducing light or a mixture of the light absorbing material and a resin. 
     
     
       13. An information recording medium according to  claim 12 , wherein the resin is at least one kind selected from polycarbonates, PMMAs, norbornen resins and cycloolefin resins. 
     
     
       14. An information recording medium according to  claim 12 , wherein the light absorbing material is at least one kind selected from carbon materials, organic coloring agents, dyes, pigments and semiconductor particles. 
     
     
       15. An information recording medium according to  claim 1 , wherein the first reflected-light reducing portion includes both a light absorbing portion having an optical characteristic of absorbing the reproducing light and a reflectance reducing portion having an optical characteristic of reducing reflectance of the reproducing light. 
     
     
       16. An information recording medium according to  claim 15 , wherein the reflectance reducing portion is disposed at an incident side of the reproducing light with respect to the light absorbing portion. 
     
     
       17. An information recording medium according to  claim 3 , wherein the reflectance reducing portion includes a dielectric film or a diffractive optical element having a sub-wavelength structure. 
     
     
       18. An information recording medium according to  claim 3 , wherein the reflectance reducing portion is formed at a side opposite to an incident side of the reproducing light with respect to the substrate. 
     
     
       19. An information recording medium according to  claim 1 , wherein the recording layer contains one kind of recording material selected from photopolymers, diarylethene and its derivatives. 
     
     
       20. An information recording medium according to  claim 19 , wherein the recording layer further contains a resin substantially transparent to the recording light and the reproducing light. 
     
     
       21. An information recording medium according to  claim 19 , wherein the recording layer contains a fluorescent material for emitting light of a wavelength for exposing the recording material upon being irradiated with the recording light. 
     
     
       22. An information recording medium according to  claim 1 , wherein the optical constant is a refractive index. 
     
     
       23. An information recording medium according to  claim 1 , wherein the recording in the recording layer is made by two-photon absorption. 
     
     
       24. An optical information recording/reproducing apparatus for recording information to and reproducing information from the information recording medium according to  claim 1 , comprising:
 a light source for emitting recording light, 
 a light source for emitting reproducing light, 
 an objective lens for focusing the recording light and the reproducing light emitted from the light sources on the information recording medium, 
 a light detector for detecting light reflected by the information recording medium, and 
 a second reflected-light reducing portion for reducing reflected light of the reproducing light transmitting through the information recording medium provided on a surface facing the information recording medium at the other side of the objective lens. 
 
     
     
       25. An optical information recording/reproducing apparatus according to  claim 24 , wherein the information recording medium has a first reflected-light reducing portion for reducing reflected light of the reproducing light from a substrate side provided at a side opposite to an incident side of the reproducing light with respect to the recording portion. 
     
     
       26. An optical information recording/reproducing apparatus according to  claim 24 , wherein the second reflected-light reducing portion has a surface inclined with respect to an optical axis of the reproducing light emitted from the light source and incident on the information recording medium. 
     
     
       27. An optical information recording/reproducing apparatus according to  claim 24 , wherein the second reflected-light reducing portion includes a light absorbing body having an optical characteristic of absorbing at least the reproducing light. 
     
     
       28. An optical information recording/reproducing apparatus according to  claim 24 , wherein the recording in the recording layer is carried out with a semiconductor laser light source for emitting a pulsed beam whose pulse width is from 100 femtoseconds to 10 nanoseconds. 
     
     
       29. An optical information recording/reproducing apparatus according to  claim 24 , the recording in the recording layer is made by two-photon absorption.